Chapter XXXV: Introduction (31)

A, rostrum.
B, carina.
S, moveable scutum, S′, scutum fixed and modified so as to
form part of the shell.
T, moveable tergum, T′, tergum fixed and modified so as to
form part of the shell.
In S, and S′, _a_ is the occludent margin; _b_, the basal
margin; _m_, the plate to which the adductor muscle is
fixed; _o_, a ledge formed during continued growth, in
the upper part of the fixed scutum, in order to keep the
orifice perfectly closed; this ledge is seen distinctly
only in fig. 5.
In S and S′ the tergal margin is marked by small dashes; (′)
being the upper articular ridge, and (′′), the second or
lower articular ridge: in S′ (′′) is called the parietal
portion of the valve.
In T and T′, the scutal margin is marked by small dashes; (′)
being the first and upper articular ridge, hardly distinct
from the occludent margin, and called in T′′ the occludent
rim; (′′) is the second or middle, and (′′′) the lower or
third articular ridge, called in T′′ the parietal portion
of the valve; _x_ is the carinal margin, called in T′ the
carinal rim, and _z_ the basal margin; _o_ is the occludent
margin: in T′, a ledge is formed across the under side
close to the apex, which ledge is necessary to keep the
orifice neatly closed, owing to the apex of the moveable
tergum coming to project freely during growth.

Fig. 1 _a_, Verruca Strömia, specimen with the left hand scutum
and tergum fixed and modified into part of the shell.
1 _b_, Verruca Strömia, (with left hand scutum and tergum
fixed), with the valves and compartments separated from
each other; the homologous parts of the opercular valves
are marked by corresponding letters and dashes.
1 _c_, Verruca Strömia, left hand scutum and tergum fixed,
viewed from the under side.
1 _d_, Verruca Strömia, _smooth var._, reversed specimen, _i.
e._, with the right hand scutum and tergum fixed and
modified into part of the shell.
1 _e_, Verruca Strömia, shell seen from the under side; the
right hand scutum and tergum (as in 1 _d_) being the fixed
pair: the moveable scutum and tergum (S, T) are seen in the
shade at the bottom of the shell, and their shape will be
best understood by looking at fig. 1 _f_. The fixed scutum
and tergum S′, T′, differ a little in shape, and in the
form of their line of junction, from the same two valves
(reversed) in fig. 1 _c_.
1 _f_, Verruca Strömia, moveable scutum and tergum, seen from
the under side, taken from a specimen, in which (as in 1
_d_ and _e_) the right hand scutum and tergum were the
fixed pair.
2, Verruca Spengleri, scutum seen from the under side, showing
the medial, prominent adductor ridge; taken from a
specimen, in which the right hand scutum and tergum were
fixed.
3 _a_, Verruca lævigata, scutum and tergum, external view of,
from a specimen in which the left hand pair was fixed; 3
_b_, scutum and tergum, internal view of, from a specimen,
in which the right hand pair was fixed.
4, Verruca prisca, scutum and tergum, external view of, from a
specimen, in which left hand pair was fixed.
5, Verruca nexa, with the valves separated, the left hand
scutum and tergum being the fixed and modified pair.
6, Portion of ribbed shell of a Venus, to which a _Verruca
Spengleri_ had been attached, showing the peculiar form of
the excavation.

PLATE 22.

ALCIPPE LAMPAS.

Fig. 1, Entire animal (female and two males) greatly magnified,
being an unusually symmetrical specimen, partly copied from
Mr. Hancock's Plate ('Annal. and Mag. Nat. Hist.' ser. 2,
vol. 4, Pl. VIII). H, horny disc and surface of attachment;
_a_, projection formed by the lower end of the lip of the
orifice leading into the sack; _m_, a pair of males, of
their proper proportional sizes, attached in their ordinary
position.
2, Entire animal, much distorted.
3, Small portion of a Fusus (copied from Mr. Hancock's Plate),
perforated by the Alcippe; the darker curved marks are the
slit-like orifices, leading into the chambers; the latter
are seen from the outside, owing to a difference of tint in
the shell of the mollusc where worn thin over the chambers;
they are represented by the fan-shaped shaded patches.
4, One of the orifices, leading into a chamber, much enlarged;
_a_, the curved narrow end, which was open and used when
the animal was young, but has since been closed externally
by sand or shelly matter, and internally by the upward
prolongation of the horny disc; _b_, rims of an inorganic,
calcareous deposit, by which the narrow end of the orifice
is kept of the due degree of narrowness.
5, Longitudinal section through the outer envelopes of a very
symmetrical specimen, giving a lateral view of the included
body.
_a_, point at the lower end of the orifice of the capitulum,
leading into the sack.
_b_, end of adductor muscle.
_c_, mass of branching ovarian cæca, much developed and
protuberant on the under side.
_d_, basal point of the quasi-peduncle, projecting beyond the
level of the horny disc (H, H).
_e_, sack or open cavity: of the two branchiæ or ovigerous
fræna, one has been removed with the outer envelopes, the
other is hidden by the projection caused by the medial
distended mass of the ovarian cæca.
_e′_, lateral line of junction of the body to the outer
envelopes; which latter have been here cut through in
removing the near half of the capitulum and peduncle.
_f_, notch separating the capitulum or upper part from the
peduncle or lower part of the external covering: this notch
varies much in depth.
_g_, the end (homologically the carinal end), of the orifice
leading into the sack, where the cutting of the outer
envelopes has commenced.
H H, horny disc, cut longitudinally down the middle.
_h_, first pair of cirri.
_i_, prosoma (homologically the second thoracic segment).
_k_, the thoracic segment, which would have borne the second
pair of cirri, had such existed.
_l_, thoracic segment, which should have borne the third pair.
_m_, thoracic segment, which should have borne the fourth
pair.
_n_, thoracic segment, very small, bearing the fifth pair of
cirri.
_n′_, fifth pair of cirri, only one cirrus on the near side
being represented.
_o′_, sixth cirrus, borne on the last thoracic segment, too
small to be shown. _p_, caudal appendages.
6, one side or lip of the orifice leading into the sack,
greatly enlarged, seen on the inner side, formed of an
inner membrane, _b_, (on which the long hairs and an S-like
band of spines, too fine to be plainly represented, are
placed), and an outer membrane _c_, studded with short,
thick spines, the corium between these two membranes having
been removed; _a_, projection at lower end of orifice;
_g_, upper end of orifice, showing the point where the
corresponding side or lip of the orifice has been cut away.
7, small portion of the external membrane, showing the
star-shaped, hard, projecting points of chitine; but they
are here placed too closely together.
8, front view of mouth, greatly enlarged, and with the
gnathites rather unnaturally separated from each other;
_h_, the first pair of cirri; in front, the outer maxillæ
appear like a bilobed lower lip; the inner maxillæ (with
their singular membranous swelling behind, see fig. 15),
can be distinguished by their long apodemes or horny
imbedded bars; behind are seen the one-toothed mandibles,
with a swelling behind, probably representing the palpi;
all above the mandibles consists of the immensely developed
labrum, with the foreshortened ends of the row of long
hairs on each side; the fold, or articulation, separating
the mouth and body, is seen crossing above the basal ends
of the apodemes of the maxillæ.
9, Lateral view of the coriaceous button or cushion, _c′_, on
one corner of the upper segment, _b_, of the pedicel of
the sixth cirrus; _c_, being the lower part of the lower
segment of the one ramus of this same cirrus: the hooked
hairs are rather distorted.
10, The same, viewed from the inner side.
11, Lateral view of the labrum, with the mandible, _m_,
attached to it, which latter, from overhanging the
œsophagus, shows the position of the mouth; _h h_, is the
first cirrus on the near side; _b_, is the medial crest of
labrum, on the side of which extends a long row of hairs;
_a a a_, delicate membrane of side of body, attached to the
margins of the labrum.
12, Diagram showing the probable manner in which the young
Alcippe bores into the shell of molluscs; _a_, pupa
attached by the antennæ to the outer surface of shell; _b_,
outline of young Alcippe soon after its metamorphosis; the
anterior or lower end has increased considerably in length,
so as to project beyond the point whence the antennæ
rise, and it has now penetrated the shell, being attached
to the roof of its incipient chamber by its horny disc,
represented by a thick black line; _c_, is the Alcippe
after further growth, when it has succeeded in burying
itself; the horny disc is now attached parallel to the
surface of the shell; the horny disc of its former state,
now lines the narrow end of the slit-like orifice leading
into the shelly chamber: the above changes in position
are supposed to have been effected quite gradually. The
diagram, _c_, I may add, represents the position of the
Alcippe for the rest of its life, the chamber being added
to at both ends, sides, and bottom.
13, Lateral view of the posterior extremity of the thorax, much
enlarged, with its articulated appendages represented only
on one side; the four thoracic segments, _l_, _m_, _n_,
_o_, correspond with those represented in fig. 5. In one
monstrous specimen, segment _n_, bore a single cirrus. The
posterior thoracic segment, _o_, bearing the sixth pair of
cirri, _o′_, is very small and obscure, and can be seen
only by separating the fifth and sixth pairs of cirri;
or by longitudinally bisecting the thorax, and viewing
the inner side; _n′_, fifth cirrus; _a_, lower segment,
_b_, upper segment of pedicel; _c_, lower, and _d_, upper
segment of the one ramus, the other ramus being represented
by the coriaceous boss _c′_; _o′_, sixth cirrus, with
similar segments; _p_, caudal appendage.
14, First cirrus.
15, Maxillæ, with the lower end of the apodeme cut off, showing
the curious membranous swelling on the side towards the
mandible.

PLATE 23.

_Genera_--ALCIPPE AND CRYPTOPHIALUS.

ALCIPPE LAMPAS.

Fig. 16, Pupa of male Alcippe lampas, viewed laterally; _a_,
antennæ, _c′_, eyes attached to the apodemes; above these
the single eye of the mature male may be distinguished.
17, Abdomen of the same; _p_, posterior end of thorax; _q_,
abdomen; _r_, caudal appendages.
18, Male of Alcippe lampas immediately after the metamorphosis,
the ventral surface being uppermost, but the specimen has
been in some way distorted, as the lobe (_i_) ought to
project on the opposite side; _a_, antennæ of the pupa;
_g_, _h_, lateral lobes; internal organs not yet formed;
orifice at upper end (_i_) not visible; scale same as for
the pupa, fig. 16.
19, Male of Alcippe lampas, when fully mature; scale same as in
last figure (18) and as in fig. 16.
_a_, antennæ of pupa.
_b_, vesicula seminalis.
_c_, _eye_, (seen in fig. 16 above the eyes of the pupa,
_c′_.)
_d_, testis.
_e_, lower transverse muscle.
_f_, upper transverse muscle.
_g_, _h_, lateral lobes of the external covering, answering
to the sides of the peduncle of the female.
_i_, terminal lobe on the ventral side of the orifice,
probably corresponding with _a_ in fig. 1, Pl. 22.
_k_, orifice of the tubular sack.
_l_, oblique muscles on the ventral side of the sack.
_m_, probosciformed penis, shown exserted; _m′_ portion
within the tubular sack.

CRYPTOPHIALUS MINUTUS.

Fig. 1, Cryptophialus minutus (female with an attached male)
viewed laterally, but with the disc (H) rather turned
towards the beholder, much enlarged; _a_, orifice leading
into the sack; H, thin horny disc by which the animal is
attached within its cavity; H′, upper free worn edge of the
disc; _z_, male attached in its usual position to the edge
of the disc of the female.
2, Cryptophialus minutus, natural size, within a half-inch
circle; this represents the largest specimen which I have
ever seen.
3, Half the orifice, with a large portion of the external
membrane and of the membrane lining the sack.
_a_, _a_, dentated horny rim of orifice.
_b_, _b_, external membrane, with the underlying corium or
true skin removed.
_b′_, a horny bar, expanding at its lower end into a toothed
plate, and at the upper end connected with the horny rim
round the orifice.
_c_, _c_, membrane lining the sack.
_c′_, horny bar by which this membrane is strengthened.
_c′′_, thickened membrane, or bar, expanding into fibrous
sheets for the attachment of a muscle.
_d_, delicate lateral lip, within the outer dentated horny
rim.
4, Orifice of sack, cut off, widely open, viewed from above;
_a_, horny dentated rim; _b′_, top of horny bar, where
united to the rim; _d_, inner lateral lip folded backward;
_d′_, lip, with coarser hairs, at the carinal end of the
orifice.
5, Animal with the outer tunics removed, viewed laterally.
_a_, dentated horny rim of orifice, continuous with
_b_, outer membrane, here cut off.
_c_, inner membrane of sack, continuous with
_c_, _c_, the reflexed membrane of the body, by which the
body is united to the disc and outer envelopes.
_e_, lancet-shaped labrum.
_e′_, projection behind the labrum.
_f_, palpi.
_g_, outer maxillæ, between which and the palpi lie the inner
maxillæ and mandibles; these latter are rather exaggerated
in size.
_h_, first maxilliped, in a rudimentary condition, close
above which is the articulation separating the whole mouth
(_o_) from the first (^1) segment of the body.
_i_, _k_, tapering appendages springing from the second and
third segments of the body.
_l_, pedicels of the three pairs of abdominal cirri.
_m_, cirri, three pairs of.
_o_, mouth, of great size, formed by the confluence of the
lower segments of the gnathites.
^1, first segment of body, homologically the last or seventh
cephalic segment.
^2, second segment of body, homologically the first thoracic
segment.
^3, third segment of body, homologically the second thoracic
segment.
^4, fourth segment of body, homologically the third thoracic
segment.
^5, fifth segment of body, homologically the fourth thoracic
segment.
^6, sixth segment of body, homologically the fifth thoracic
segment.
^7, seventh segment of body, homologically the sixth thoracic
segment.
^8, eighth segment of the body, homologically the seventh
thoracic segment.
6, Front of mouth; _g_, outer maxillæ; _g′_, an articulation
separating the mouth from the membrane of the first segment
of the body; _h_, first pair of maxillipeds; whole figure
on same scale with the labrum, fig. 9.
7, Maxillæ, drawn on thrice the scale as the outer maxillæ;
_a_, apodeme.
8, Mandibles, drawn on thrice the scale as the outer maxillæ.
9, Labrum, on same scale with the outer maxillæ, fig. 6, and
one third of the scale of the mandibles and inner maxillæ;
_e_, labrum; _f_, palpi.

PLATE 24.

_Genera_--CRYPTOPHIALUS AND PROTEOLEPAS.

CRYPTOPHIALUS MINUTUS.

Fig. 10, Lower enlarged end of œsophagus, where entering the
stomach, viewed from one of the sides bearing the discs
of teeth; _a_, upper cut off end of œsophagus; _b_, the
lower end and natural opening; _c_, thickened rim, having a
somewhat beaded structure.
11, The same; diagram giving a transverse section of the
above in the line of the discs of teeth; _c c c c_, four
thickened beaded edges; _e e_, two other but narrower and
less prominent beaded edges; _d d_, discs of teeth; _f_,
rows of fine bristles; the almost double row of bristles on
each side under (_d_) is not of course seen in this section.
12, Lower end of œsophagus viewed from a position at right
angles to that in fig. 10; or from the side _e_, of the
diagram, fig. 11; the two discs of teeth are consequently
shown in profile; _a_, upper cut off end of œsophagus; _b_,
lower natural end; _c_, _c_, thickened edges; _e_, narrower
thickened edge, projecting towards the beholder; _d_, disc
of teeth seen in profile.
13, Portion of one of the cirri; _a_, lower segment of pedicel;
_b_, upper segment, supporting the two rami.
14, Segments of one of the rami much enlarged; _a_, thickened
shield-like portion of membrane.
15, Ovum, (thirty-five times the natural size.)
16, Egg-like larva in the first stage, on same scale.
17, " " in the second stage, on same scale.
18, Larva in the last or pupal stage, on four times the scale
of fig. 15-17; _a_, antennæ; _b_, apodeme and eyes; _c_,
abdominal bristles. A male would have been developed from
this pupa.
19, Male on same scale as the pupa, fig. 18; _a_, three
terminal segments of the antennæ of the pupa; _d_, orifice
of the sack.

PROTEOLEPAS BIVINCTA.

Fig. 1, Antenna of the pupa (three terminal segments of), with
a portion of one of the two threads, enclosing the
cement-ducts, by which the body of the Proteolepas is
attached; the upper portion of the thread, and the
adjoining part of the body, are represented in section.
_a_, part of the great mass of cellular matter within the
ovarian sack, in process of development into ova, and
changing its character as soon as it enters the tube or
cement-duct.
_b_, membrane forming the ovarian sack and the cement-ducts,
the latter enclosed within the threads of attachment.
_c_, corium lining the outer membrane of the body, and the
upper part of the threads.
_d_, outer membrane of body.
_e_, " " becoming suddenly thicker where
forming the outer membrane of the thread.
_e′_, outer membrane of the thread in the lower part, here
not shown in section.
_f_, main or second segment of the pupal antenna, the basal
segment having, as in all cases, been moulted, with the
carapace of the pupa.
_g_, disc-segment, apparently with a small orifice for the
issuing of the cement.
_h_, terminal segment with the shorter spines broken off.
2, Compounded mandibular organ, sketched by the camera; _a_,
supposed mandible; _b_, perhaps portion of the mandible;
_c_, maxilla; _d_, ligamentous fibres giving attachment to
muscles.
3, Mouth seen from the ventral side, sketched by the camera;
_r_, articulation separating the mouth from the body;
_c_, compounded mandibular organ; _d_, palpus, united to
the opposite palpus and to the crest of the labrum; the
latter forming the back of the hollow in which the compound
mandibles work.
4, Diagram of the mouth of an ordinary cirripede, seen from
above; _a_, outer maxilla; _b_, maxilla; _c_, mandible;
_d_, labrum.
5, Diagram, illustrating the supposed changes in _position_ of
the gnathites in Proteolepas, causing them to stand back
to back; _a_, outer maxilla; _b_, maxilla; _c_, mandibles;
_d_, labrum.

PLATE 25.

_Genera_--PROTEOLEPAS AND BALANUS.

PROTEOLEPAS BIVINCTA.

Fig. 6, Proteolepas bivincta: diagram, showing the probable
position of the young animal, just before its
metamorphosis, within the carapace of the supposed pupa;
_a_, caudal appendages; _b_, six pairs of natatory thoracic
legs; _c_, mouth, no doubt closed and functionless, as in
other pupæ; _g_, threads of attachment, with cement-ducts
in process of formation; _h_, antennæ.
7, Proteolepas bivincta, magnified about twenty-six times.
_m_, mouth, the summit being formed of the labrum and palpi
joined.
_^{1}c_, first segment of body; homologically the seventh or
last cephalic segment.
_^{2}t_ to _^{8}t_, second to eighth segment of body;
homologically, first to seventh thoracic segments.
_^{9}a_ to _^{11}a_, ninth to eleventh segment of body;
homologically, three segments of abdomen.
_d′_, three muscles attached on each side to the labrum, and
running to the gnathites.
_e e_, great ovarian sack.
_f_, true ovaria.
_g_, threads of attachment.
_h_, three terminal segments of the antennæ of the pupa.
_i_, vesicula seminalis.
_k_, papilla representing the penis.

Fig. 1, _Balanus tintinnabulum_: an enlarged longitudinal section
through the shell and sack, with the right-hand scutum and
tergum and right-hand half of shell and basis removed,
exhibiting the body of the animal not in section. The cirri
are exhibited only on one side.
A, A, orifice of shell, within which lies the operculum
formed by a pair of scuta (S), and pair of terga (T).
B, basis (homologically the anterior end of the shell).
K, carina of shell (or dorsal valve or compartment of shell).
K′, sheath of carina.
L, lateral compartment of shell. The carino-lateral
compartment is hidden by the scutum and tergum.
R, rostrum of shell (or ventral valve or compartment of
shell).
R′, sheath of rostrum.
O, O, opercular membrane, connecting the opercular valves
with the overhanging basal edge of the sheath.
S, scutum.
T, tergum.
_a_, adductor scutorum muscle, with the scutum on the near
side removed.
_b_, the whole space enclosed by a broken sinuous line, round
_a_ and _b_, shows the cut surface of attachment to the
near scutum, which has been removed.
_b′_, lower muscle, on the near side, running from near the
basal edge of the scutum to near the basal margin of the
labrum (_e_). Above this are three other muscles (all on
the near side), running to the membrane between the labrum
and adductor muscle.
_c_, prosoma, including the main portion of the stomach and
thickened ends of the vesiculæ seminales: homologically
this is formed by the development of the second thoracic
segment, which carries the first pair of cirri; and
possibly, in part, by the antecedent segment, _i. e._ the
first thoracic segment.
_c′_, thorax, extending from the prosoma to the posterior
end of the body: the letter (_c′_) stands on the segment
supporting the third cirrus; homologically, this segment is
the fourth thoracic.
_d′_, orifice of the acoustic sack, above which is the basal
articulation of the first cirrus.
_e_, labrum, forming the back (_i. e._ anterior end) of the
mouth, with the transverse palpi obscurely seen on the
summit.
_f_, sack in which the animal lies, with the tunic lining
it, continuous with that investing the prosoma (_c_), and
lining the under sides of both opercular valves, but cut
off round (_b_) and (_a_) by the removal of the near
scutum. The branchia on the further side, which occupies
the position represented at fig. 3, is covered by the body
of the animal.
_g g_, ovarian, inosculating cæca, branching from the simple
duct (of which the near one of the pair is represented),
leading to the ovaria (not represented) within the body.
_h_, rostral depressor muscle of the scutum: the lateral
depressor muscle of the scutum is hidden by the body and by
the membranes of the sack.
_i_, carinal depressor muscle of the tergum.
_z_, antennæ (three terminal segments) of the pupa; I
distinctly saw these in this species, but they are here
represented considerably too large, even on the supposition
that a young shell had been drawn, and magnified about
twelve times.
2, Testes of _Balanus perforatus_, greatly magnified.
3, Branchia of _Bal. tintinnabulum_, on the same scale as in
fig. 1, and in its natural position. This drawing was made
by lifting up the body in fig. 1; the organ being thus
completely exposed over its whole interior surface; _a_ is
the basal end of the spur of the tergum.

PLATE 26.

STRUCTURE OF THE MOUTH AND THORAX.

N.B.--_The same letters of reference are used for the parts of the
mouth throughout this plate. All the organs here represented have
been cleaned by boiling in potash, and consist exclusively of the
external membrane._

Fig. 1, Mouth of _Balanus perforatus_, viewed from vertically
above, with the first pair of cirri _x x_ in their proper
position, cut off close above their basal articulations.
_a_, outer maxilla; _a′_, ditto, cut closely off.
_b_, maxilla.
_c_, mandibles.
_d_, palpus; _d′_ ditto, cut closely off.
_e_, labrum, crest of.
_x x_, first pair of cirri, cut off.
2, Supra-œsophageal cavity of the mouth of _Balanus
improvisus_, torn open, with the palpi, mandibles, and
maxillæ removed, exhibiting the inner face of the labrum,
laid flat, and the inner faces of the outer maxillæ; scale
as in fig. 1.
_a_, outer maxillæ; _a′′_, inner and lower lobe of ditto.
_d′_, point of attachment to the torn-off palpus.
_e_, labrum, crest off; _e′_, central notch, with graduated
teeth on both sides.
_f_, triangular thickened portion of the inner fold of the
labrum; _f′_, rib or bar of membrane, thickened to support
the surrounding very thin membrane of the supra-œsophageal
cavity.
_g_, opening of the œsophagus.
_h_, forked bar of thickened membrane, for same purpose as
_f′_.
3, Mouth of _Coronula balænaris_, divided vertically in a
transverse line, with the outer and inner maxillæ and
mandible on the left side removed, with the labrum, the
other mandible and both palpi viewed on the inside, and
with the œsophagus adherent in its proper position.
_c_, Mandible, upper free segment; _c^1_, second or middle
segment; _c^2_, supposed third or basal segment, forming
the basal margin of the mouth, but not separated by any
articulation from the labrum.
_d d_, palpi; _d′_, aperture, through which the inside of
this palpus can be seen, caused by the mandible having been
cut off; the membrane on the under side of this aperture
is thickened, and affords the chief support to the palpus;
_d′′_, thin membrane, apparently part of the palpus,
connecting the attached basal end of the palpus to the
externo-lateral surface of the mandible.
_e′_, central notch in the crest of the labrum; _e′′ e′′_,
basal margin of the labrum, to which the membrane of the
body is joined.
_f_, thickened portion of membrane, part of the inner fold of
the labrum, corresponding with _f_ in fig. 2.
_g_, orifice of the œsophagus, with the front part of the
supra-œsophageal cavity cut away; _g′_, lower, expanded, or
bell-shaped, end of the œsophagus, in its natural condition.
_i_, _k_, concavities for the attachment of muscles running
to the mandibles.
_m_, cut off edge of membrane forming the side of the mouth,
which cut edge can be followed up above the aperture _d′_,
where the upper basal end of the palpus has been cut off,
and so onwards by _g_, to the mandible on the opposite side
of the mouth.
4, Mouth of _Coronula balænaris_, viewed from the outside, in
front, with the inner maxilla, mandible, and palpus on
the left side of the figure, and nearly the whole labrum,
and the greater part of the palpus on the right side, all
cut away. The maxilla, mandible, and basal portion of the
palpus on the right hand, are pulled out of their proper
positions; for the toothed edge of the mandible ought to
have stood higher, and nearly in a line between and behind
the outer maxillæ, and then the basal margin _e′′_ of the
lateral portion of the labrum would be raised, and curling
round, would stand nearly where the letter _b′_ is now
placed.
_a_ _a_, outer maxilla, upper _free_ lobe; _a′′_, lower
and inner _free_ lobe; _a^1_, supposed second or middle
segment; _a^2_, supposed third or basal segment; _a′′′_,
basal articulation of mouth, separating it from the ventral
surface of the thorax.
_b_, inner maxilla; _b′_, apodeme of do.
_c_, mandible, upper free segment; _c^1_, second segment;
_c^2_, third and basal segment, but not separated by an
articulation from the labrum.
_d_, palpus; _d′′_, membrane uniting the basal end of the
palpus, where attached to the labrum, to the side of the
mandible.
_e′′_, basal margin of the labrum, on one side, displaced and
pulled down.
_n_, orifice of the olfactory pouch.
5, _Balanus amaryllis_: mandible, upper free segment, seen
from the side that faces the labrum; _p_, an arched line,
where the thickened membrane of the upper free part
terminates, and is united by thin membrane to the near side
of the palpus; _q_, ligamentous bands for the attachment of
muscles.
6, _Balanus amaryllis_: palpus, on the same scale as the
mandible, fig. 5, seen from the outside, so that the
further or under face is the side which, towards the right
hand, is united to the near face of the mandible, fig. 5;
_r_, long bristles, springing from a protuberance near
the extremity; these bristles, in many species, form a
long single row, parallel to the basal margin; _s_, upper
row of shorter bristles; _t_, row of very short bristles,
arising from the further side and curling over the crest of
the labrum.
7, _Balanus amaryllis_: maxilla on twice the scale of the
mandible and palpus; _b_, upper free segment; _b′_,
apodeme; _b^1_, thickened portion of membrane, perhaps
answering to the second segment of the mandibles; _b^2_,
thin membrane, extending down to the basal edge of the
mouth, possibly answering to the basal segment of the
mandibles; or perhaps the thickened membrane forming the
protuberance _c^2_ in fig. 3, may be considered as the
basal segment of the maxillæ.
_u_, step-formed projection at lower angle of maxilla.
8, Thorax of _Coronula diadema_: outer membrane of the five
posterior segments laid almost flat, and viewed externally
as a transparent object.
^2 to ^6, the second to the sixth cirrus, cut off a little
above their basal articulations.
_a_, basal curved end of the probosciformed penis.
_b_, anus; _b′_, the membrane surrounding the anus, probably
consisting of a rudiment of the abdomen.
_c_, rectum, _seen through on the under side_.
_d_, basal articulation of the sixth cirrus; _d′_, do. of the
fifth cirrus; _d^2_, do. of the second cirrus.
_e e′_, posterior thoracic segment, carrying the sixth pair
of cirri; the dorso-lateral portion _e_ is separated, in
this one segment, from the corresponding portion _e′_ by a
narrow slip of thinner membrane, which may be a part of the
abdomen let in.
_e^2 e^2_, thoracic segment, supporting the second pair of
cirri.
_f_, _f^3_, folds or articulations between the adjoining
segments.
_g_, swollen, punctured portions of membrane, not differing
homologically from the rest of the segments.
_h_, posterior portion of the prosoma, or the specially
enlarged part of the thorax; it carries the first pair of
cirri; homologically _h_ forms part of the second segment
of the thorax of the archetype Crustacean.

PLATE 27.

NERVOUS SYSTEM AND SENSES.

Fig. 1, Nervous system of _Coronula diadema_, seen from the
ventral surface.
A, infra-œsophageal ganglion; two pairs of rather small
nerves, arising from the dorsal surface, cannot be here
shown.
B, supra-œsophageal ganglion, double.
C, ophthalmic ganglion, single.
D D, eyes, as believed to exist.
_a_, three pairs of nerves, running to the gnathites and
olfactory pouches;
_a′_, nerve rising from the collar, running towards the
mandibles.
_b_, single medial nerve, running to the great transverse
muscle, extending across the upper part of the stomach.
_c_, collar-nerve or chord, uniting the infra- and
supra-œsophageal ganglions.
_d_, great splanchnic nerve, here spread laterally out, but
properly running along the sides of the upper part of the
prosoma, and therefore under the collar-nerve;
_d′_, plexus by which this nerve is connected with the
supra-splanchnic nerve, _e_.
_e_, supra-splanchnic nerve, rising from the collar, almost
in contact with the supra-œsophageal ganglion;
_e′_, small nerve rising from the end of the supra-œsophageal
ganglion, and running to the adductor and surrounding
muscles.
_f_, _f_, pair of great nerves (_antennular_), distributed
over the sack and shell.
_g_, chord (in appearance single), uniting the
supra-œsophageal ganglion with the first (C), or ophthalmic
ganglion.
_h_, small medial nerve, running to near the adductor muscle.
_i_, nerve supposed to run from the ophthalmic ganglion to
the eye.
_k_, small nerve, rising from the main ganglion (A), between
_r^1_ and _r^2_, or the nerves running to the first and
second pairs of cirri.
_œ_, position of the œsophagus.
_r^1_ nerve entering the first cirrus.
_r^2_, _r^3_, _r^4_, _r^5_, _r^6_, nerves entering the five
succeeding pairs of cirri.
_s_, nerve entering the probosciformed penis.
2, nervous system of _Balanus tintinnabulum_; letters of
reference as in fig. 1.
3, acoustic sack of _Balanus tintinnabulum_.
4, " " _Coronula diadema_.
5, eye of _Balanus tintinnabulum_; _i_, nerve coming from the
ophthalmic ganglion; D, eye itself.

PLATE 28.

CEMENTING APPARATUS.

Fig. 1 _a_, Basal membrane, with the cementing apparatus, of
_Coronula balænaris_; a small portion of the parietal
membrane, _p p p_, which coats the folded shelly walls, is
left adherent to the basal membrane.
_b_, the circumferential slip (shaded more darkly than the
rest to catch the eye), separating the basal from the
parietal membrane.
_c′ c′_, slips of basal membrane, formed at each period of
growth, and overlapping each other.
_s s s s s s_, the six sutures in the walls, separating the
six compartments, of which--
A is the basal margin of the rostrum,
C C that of the lateral compartments,
D D that of the carino-lateral compartments, and
E that of the carina.
_r_, _r_, rays or spokes of membrane, prolonged from the
circumferential slip, and running under the trebly folded
wall of each compartment, but here cut off; a similar ray
should run under each line of suture (_s_). These rays, at
their extremities, expand transversely; and the shape and
length of the rays may be judged of from the basal outline
of the folded walls given in Pl. 16, fig. 5.
The two cement-ducts, proceeding from each cement-gland,
debouch opposite the middle folds of the lateral (C C)
and carino-lateral (D D) compartments. The layers of
cement have been removed. N.B. There is one considerable
error in this figure, the two main trunks, connecting
the cement-glands, and meeting at the centre, have been
represented as forming a straight line, but in fact they
form a very open angle, as is correctly shown in fig. 1 _c_.
1 _b_, Diagram, representing a vertical section through a
portion of the basal and parietal membranes, with the
thickness of the membrane enormously exaggerated.
_z z z_, layers of cement, which, if the section had been
made in the line of the cement-ducts, would have been seen
proceeding out of these ducts, as is represented at (_t_),
where the section is supposed to have taken the above
course.
_c′ c′_, the slips of basal membrane.
_b_, the circumferential slip; beneath this the coarsely
dotted layer represents the cement, lately excreted, and
before it has acquired its proper transparent structureless
character, elsewhere represented by fine dots.
_p_, membrane externally coating the walls of the shell.
_t_, cement-ducts opening beneath the basal membrane.
1 _c_, The central portion of fig. 1 _a_, considerably
magnified.
_c′ c′_, slips of the basal membrane; but the shell, when
these were formed, was so young that the walls had not
acquired their folded structure; in the centre the
prehensile antennæ of the pupa may be obscurely seen.
_f_, the main cement-trunk, connecting the cement-glands.
_h_, a cement-gland, from which two cement-ducts proceed.
_a a_, cement-ducts (cut off), leading to opposite the middle
fold of the carino-lateral compartment.
_b b_, cement-ducts (cut off), leading to opposite the middle
fold of the lateral compartment.
_a′ b′_, a pair of cement-ducts, with their orifices opening
on the under side of one of the slips of basal membrane
(_c′_), at a point which once was opposite the middle of
the carino-lateral and lateral compartments. The orifices
of the other ducts, towards the centre, may be seen forming
straight lines.
2, Cement-ducts and one cement-gland of _Chelonobia patula_,
represented without the basal membrane, to which they
adhere: _f_, _f_, main cement-trunk; _g_, enlarged portion;
_h_, gland; _a_, _b_, the two ducts proceeding from this
gland, and bifurcating several times before debouching
on the under side of the basal membrane. Several other
cement-ducts, proceeding from other glands, are represented
just as they appeared under the microscope.
3, Cement-ducts and glands of _Tubicinella trachealis_,
represented without the basal membrane to which they
adhered: (_f_) (_f_), main cement-trunk, connecting the
several glands; _h_, cement-gland; _a_, cement-duct, with a
singular loop (_a′_) having two projections or rudimentary
branches; _b_, spur or rudiment of a second cement-duct;
_c_, third cement-duct.
4 _a_, Chain of cement-glands of _Balanus tintinnabulum_,
_with all the ducts removed_, _excepting those proceeding
from the last formed gland_, which latter correspond in age
with the last-formed zone of the shelly basis; the whole of
the basis having been removed by acid.
_f_, main cement-trunk connecting the glands.
_gh_, last-formed cement-gland.
_k_, _t_, two cement-ducts, proceeding from a great common
duct; one of these bifurcates at (_t_), and one branch
joins at (_t′_) the corresponding branch from the
corresponding gland.
_i i i_, circumferential duct, into which the ducts _k_, _k_,
_t_, _t_, _t′_ all enter.
_i′ i′_, branches proceeding from the circumferential duct,
which branch and sub-branch till they form a sheet (_z z_)
of cement-tissue on the outside of the basis of the shell.
4 _b_, two cement-glands of _Bal. tintinnabulum_ (this figure,
to match with 4 _a_, ought to have stood upside down),
taken from near the centre of the basis, greatly enlarged;
(_f f_), main trunk; (_g_), enlarged portion of the trunk;
(_h_), gland; _k_, _t_, two cement-ducts proceeding from a
common point, one of them (_t_) bifurcates, and gives off
a rudimentary branch, _t′_; _m_, a spur, or rudimentary
duct. The gland, _h_, has been pushed on one side, it
ought to lie over the enlarged portion (_g_). There is a
considerable difference between these two glands and that
(_gh_) represented in fig. 4 _a_; the neck of the gland in
the latter being elongated into a great common duct, and
the spur or rudimentary duct (_m_) being absent.

PLATE 29.

CIRRI AND LARVÆ, FIRST STAGES.

Fig. 1, Sixth cirrus of _Balanus amphitrite_ (_var._ cirratus),
showing the muscles.
_a_, _b_, flexor and extensor muscles, moving the upper
segment (_i_ to _k_) of the pedicel.
_c_ and _d_, flexor and extensor muscles, apparently moving
the lower segments of both rami, as a whole; the lower
articulations in these rami being confluent.
_e_ and _f_, flexor and extensor muscles extending up both
rami (those only in the near ramus being figured) to their
tips.
_g_ _g_, flexors of the separate segments in both rami.
_h_, basal articulation of lower segment of the pedicel.
_i_, upper articulation of lower segment of the pedicel.
_k_, upper articulation of upper segment of pedicel.
2, Fourth cirrus of _Acasta sulcata_.
_i_, upper articulation of the lower } _These two letters
segment of pedicel. } apply to all the
_k_, upper articulation of the upper } figures 1 to 6._
segment of pedicel. }
_l_, curved teeth on the pedicel.
_m_, " " on the segments of the anterior ramus.
3, Third cirrus of _Chthamalus antennatus_.
4, Second cirrus of _Balanus perforatus_, viewed exteriorly and
laterally.
5, Third cirrus of _Xenobalanus globicipitis_.
6, Sixth " " "
7, Spermatozoa (copied from Mr. C. Spence Bate, in 'Annals and
Mag. of Natural History' (S. 2), vol. viii, Pl. VIII).
_a_, of _Verruca Strömia_, in an early condition.
_b_, of _Balanus balanoides_, more mature.
_c_, of _Balanus perforatus_, apparently mature.
8, Larva of _Scalpellum vulgare_, immediately after coming out
of the egg, seen on the ventral surface (letters of
reference given below).
9, Larva of _Balanus balanoides_, immediately after coming out
of the egg, seen on the ventral surface, copied from Mr. C.
Spence Bate's drawing in 'Annals and Magazine of Natural
History' (S. 2), vol. viii, Plate VI, fig. 1 (letters of
reference given below).
10, Larva of _Chthamalus stellatus_, after the first moult, but
during the first stage, seen on the ventral surface,
copied; with some alterations, from Mr. C. Spence Bate's
drawing in 'Annals and Magazine of Natural History' (2
Ser.), vol. viii, Plate VIII, fig. 13.

(_The following letters apply to above figs. 8, 9, 10._)
_a_, eye.
_b_, first pair of antennæ, not observed in fig. 9.
_b′_, the same antennæ, as yet encased (in fig. 8) within
small horns.
_c_, horns, including the second pair of antennæ.
_d_, mouth, probosciformed: in fig. 8, the specimen having
been acted on by potash, the œsophagus can be seen within,
with the orifice beneath the swelling, which latter perhaps
answers to the labrum.
_e_, first, uniramous natatory leg (homologically the second
thoracic limb).
_f_ _g_, second and third, biramous natatory legs
(homologically the third and fourth thoracic limbs.)
_h_, posterior point of carapace.
_i_, forked terminal projection of the body or abdomen.
_l_, second forked projection.
_m_, two sharp points, apparently representing a third forked
projection.
_n_, a rounded swelling, apparently lying between the
carapace and the supposed abdomen, and believed to form the
anus.

PLATE 30.

LARVÆ OF LEPAS: SECOND AND LAST STAGES OF DEVELOPMENT.

Fig. 1, Larva of Lepas in the second stage of development; _a_,
supposed antennæ (second pair); _m_, mouth; _c_, three
pairs of legs. (Copied from Burmeister's 'Naturgeschichte
der Rankenfüsser,' Tab. 1, fig. 3.)
2, _Lepas australis_: pupa or larva (2 _a_, of natural size) in
the last stage of development, with the young cirripede in
its natural position, obscurely seen within,--the specimen
having been treated with caustic potash, _and so rendered
transparent_,--viewed laterally and greatly enlarged.
Scarcely more than the outline of the shell or carapace is
represented. The darkly shaded part to the left represents
the extent of the sack of the pupa, or the cavity occupied
by the thorax, with its limbs.
_a_, both antennæ, adhering by their discs to a piece of wood.
_b_, dorsal surface of the shell or carapace; and immediately
underneath this letter is the point of reflection of the
membrane investing the thorax, so as to line the sack of
the pupa.
_b′_, is the posterior end of the animal, and of the orifice
on the ventral surface, through which the legs are
protruded.
_c_, six pairs of natatory legs.
_d_, pair of caudal appendages, seated on a minute abdomen.
_m_, mouth, from which the œsophagus can be seen running into
the stomach, the latter having two dark cæca; the stomach
sweeps round in the pupa to the abdomen, near _b′_; but in
the young included cirripede, only as far as the letter
(_b_), where the bases of the posterior pair of cirri and
the anus lie.
_n_, apodemes, supporting the eyes, produced deeply inwards
from the eye-bearing segment (N, in fig. 4) of the antennæ.
_s_, bottom of sack of the young cirripede immediately after
its metamorphosis; it extends as far as _s′_. (See _s_, in
fig. 3.)
_t_, gut-formed cement-gland (or incipient ovaria), seen on
the near side of the animal, whence a cement-duct, _t′_,
runs into the near antenna.
_u_, internal and anterior part of the pupa, filled with
pulpy, oily matter, together with the incipient muscles of
the peduncle; when stretched out it forms the peduncle of
the young cirripede. See _u′_, in fig. 3.
_x_, bases of the pedicels of the cirri of the young included
cirripede.
2 _a_, Pupa of _Lepas australis_ of natural average size,
within a half-inch wide.
3, Young cirripede (on a smaller scale than Fig. 2),
immediately after the exuviation of the bivalve-like
pupal carapace, the basal segments of the antennæ, the
eye-apodemes and eyes. The young cirripede has just assumed
its proper position at nearly right angles to what it held
whilst packed within the pupa,--this change of position
having been effected by the opening out or stretching of
the deep fold of membrane (see _n_, in fig. 2) formed
over the eye-apodemes and eyes, previous to the act of
exuviation.
_a_, the three terminal segments of the antennæ of the pupa,
still remaining cemented, in the same position as before,
to the same piece of wood: the basal, or eye-bearing
segment (N, in fig. 4), has been moulted with the pupal
carapace.
_c_, _d_, legs and caudal appendages of the pupa, not as yet
moulted, but quite functionless; the external membrane of
the thorax, and that lining the sack of the pupa, are,
likewise, as yet retained, but soon will be cast off.
_s_, bottom of the sack of the young cirripede, which can now
be easily distinguished.
_u′_, the peduncle.
_x_, _y_, _z_, primordial valves, composed of chitine: _x_,
being the scutum; _y_, the tergum; _z_, the carina.
3 _a_, small portion of one of the primordial, non-calcified
valves, much magnified.
4, ventral surface of pupa; on the same scale, and in the same
semi-transparent condition as in fig. 2.
_a_, antennæ.
_b_, limit of sack on the sides in the ventral or lower half
of the pupa.
_b′_, posterior end of the carapace.
_c_, _d_, bristles of the natatory legs and of the caudal
appendages, protruded through the orifice of the carapace.
_e_, orifice of the acoustic sacks.
_m_, mouth, with the œsophagus attached to it, obscurely seen
through the carapace; the stomach having been removed.
_n_, apodemes supporting the eyes.
N, the eye-bearing or basal segments of the antennæ.
_o_, the second or main segment of the antennæ.
_p_, the third or disc segment of the antennæ.
_v_, the fourth or terminal segment of the antennæ.
W, ventral surface, bordered by the edges of the carapace;
the letter stands near the extremity of the œsophagus.
5, First pair of natatory legs: _f_, lower segment of pedicel;
_g_, upper segment of pedicel; _h_, lower segment of ramus;
_i_, upper segment of ramus; _k_, outer ramus; _l_, inner
ramus of same leg; _r_, sternal surface between the first
and second pairs of legs, with singular thickened ridges
and folds.
6, Abdomen with two caudal appendages: ^1, first abdominal
segment, attached to the posterior thoracic segment; ^2,
second abdominal segment; ^3, third or last abdominal
segment; _h_, lower segment; _i_, upper segment of caudal
appendage.
7, Transverse section of the pupa, close to the eye-apodemes;
these being made to stand more upright than in fig. 2. The
internal organs of the animal have all been removed.
_a a a′_, section of carapace; from _a_ to _a′_, on the lower
side, forms the ventral surface, with three longitudinal
furrows, here in some degree opened out.
_c_, crest of thick membrane on each side, forming the sides
of the lateral furrows.
N, the posterior margin of the eye-bearing segment (see fig.
4) of the antennæ; the edges of which are hardened and
thickened, and are produced inwards, forming
_n_, the apodemes, to which are attached the (_n′_) great
compound eyes.
8, Terminal portion of an antenna, greatly magnified, seen
from above.
_o_, part of the second or main segment; an oblique line
shows a line of separation of the upper thinner and lower
thicker membrane; _o′_, single spine borne at this segment.
_p_, disc-segment, bearing seven spines; _p′_, an irregular
border of the cement-tissue, believed to have debouched
through the spoke-like minute tubes seen on the disc.
_v_, terminal segment, projecting almost rectangularly
outwards; _v′_, most delicate tube or ribbon, believed to
consist of cement-tissue.

ERRATA.

Page

104, thirteen lines from bottom, _for_ "_Balanus elongatus_," _read_
"_Balanus galeatus_."

105, six lines from bottom, _for_ "_Balanus elongatus_," _read_
"_Balanus galeatus_."

174, Since the table on the distribution of the fossil species was
drawn up, I have examined some more specimens, sent me by Mr.
Wood, which show that _Balanus concavus_ and _Hameri_ are found
in the Red Crag; and that _Verruca Strömia_ is found in the
Coralline Crag; this will make the total in the Coralline Crag
ten, and in the Red Crag eight. I should, however, add, that
the identification of _Verruca Strömia_ in the two Crags is
a little doubtful, as the specimen was without the opercular
valves.

235, to _Fossil_ localities of _Bal. concavus_, add Red Crag
(Sutton) Mus. S. Wood.

255, six lines from the top, _Bal. crenatus_, I have now seen a
single Red Crag specimen .5 of inch in basal diameter.

278, to _Fossil_ localities of _Bal. Hameri_, add Red Crag (Sutton)
Mus. S. Wood.

293, nineteen lines from the top, _for_ "Cotantin," _read_
"Cotentin."

300, ten lines from bottom, _for_ "parieted" _read_ "parietal."

INDEX.

N.B. The names in _italics_ are synonyms or doubtful species.

Abdomen of the Balanidæ, 65.
of larvæ in first stage, 108.
in pupa of Alcippe, 548.

Abdominalia, order of, 21, 563.

Acasta, sub-genus, 302.
cyathus, 312.
fenestrata, 316.
glans, 314.
lævigata, 315.
_Montagui_, 308, 492.
purpurata, 318.
_spinulosa_, 321.
spongites, 308.
sporillus, 319.
sulcata, 310.
_tubulosa_, 320.
undulata, 313.

Acorn shell, 33.

Adductor scutorum, 53.

_Adna_, genus, 354.
_Anglica_, 360.

Affinities of the Balanidæ, 152.

Alæ, structure of, 37, 47.

Alcippe, genus, 529.
lampas (female), 530.
lampas (male), 555.
sexes of, 23.

Anelasma, false, resemblance to Xenobalanus, 445.
compared with Alcippe, 528.

Antennæ of larva in first stage, 105.
of pupa, 114.
of Alcippe, 549.
of Cryptophialus, 581.
of Proteolepas, 601.

Anus, 87.
none in Proteolepas, 596.
none in the male Alcippe and Cryptophialus, 546, 562, 585.

Apoda, order of, 22, 587.

Apodemes for the attachment of eyes of pupa, 120, 126.

Apparatus, cementing, 133.

Appendages, caudal, 65, 85, 479, 481, 491.
in Verruca, 510.
in Alcippe, 543.
filamentary, to sack, 64.
to limbs, 64, 83.

_Asemus_, genus, 321.
_porosus_, 329.

_Astrolepas_, genus, 382.
_lævis_, 396.
_rotundarius_, 392.

Attachment of Chelonobia to turtles, 390.
of Coronula to whale's skin, 411.
of Tubicinella, 436.

Baer, Von, on morphological differentiation, 19.

Balanidæ, family of, 33.
highest Cirripedes, 20.

Balaninæ, sub-family of, 175.
characters of, 152.

Balanus, genus, 177.
shell of, immediately after the metamorphosis, 41.
supposed male of, 271.
Ajax, 214.
allium, 281.
amaryllis, 279.
_amphimorphus_, 494.
amphitrite, 240.
_angulosus_, 256.
_arctica patelliformis_, 256.
_arcticus_, 262.
_balænaris_, 415.
balanoides, 267.
pupa of, 130.
monstrous specimens with imperforate penis, 102.
cementing apparatus of, 146.
_balanoides_, 240, 493.
bisulcatus, 293.
_Blainvillii_, 231.
_borealis_, 262.
calceolus, 218.
_candidus_, 277.
Capensis, 209.
_carbonarius_, 492.
cariosus, 273.
_cassis_, 218.
cepa, 283.
_chelytrypetes_, 394.
_clavatus_, 261, 267.
_circinnatus_, 492.
_communis_, 231, 492.
concavus, 235.
_cornubiensis_, 231.
corrugatus, 254.
_Coquimbensis_, 227.
_costatus_, 493.
_Cranchii_, 231.
_crassus_, 195, 493.
crenatus, 261.
_crispus_, 494.
_cylindraceus_, 206, 235, 494.
cymbiformis, 221.
_Cumingii_, 335.
declivis, 275.
decorus, 212.
_delphinus_, 494.
_dentiformis_, 493.
_diadema_, 417.
_discors_, 227.
dolosus, 295.
_d'Orbignii_, 195.
_duploconus_, 365.
eburneus, 248.
_elongatus_, 220, 261, 267.
_erisma_, 296.
_fasciatus_, 201.
_Finchii_, 492.
_fistulosus_, 267.
flosculus, 290.
galeatus, 104, 105, 220.
_geniculatus_, 256.
_gigas_, 210.
_glacialis_, 261.
glandula, 265.
_goissopomo_, 495.
Hameri, 277.
_Holgeri_, 492.
_humilis_, 495.
imperator, 288.
improvisus, 250.
inclusus, 299.
_intertextus_, 518.
lævis, 227.
_lævis_, 495.
_latiradiatus_, 493.
_miser_, 235, 494.
_Montagui_, 308.
navicula, 221.
nigrescens, 210.
nubilus, 253.
_ornatus_, 493.
_ostrearum_, 492.
_ovularis_, 267, 494.
patellaris, 259.
_patellaris_, 494.
_pectinarius_, 493.
_peregrinus_, 492.
perforatus, 231.
upfilled parietal tubes of, 44.
_perforatus_, 494.
_perplexus_, 296.
_picos_, 206.
_pictus_, 493.
_plicarius_, 493.
_plicatus_, 337.
pœcilus, 246.
_polythalamius_, 392.
porcatus, 256.
_porosus_, 493.
_proteus_, 492.
psittacus, 206.
_punctatus_, 267, 493.
_puncturatus_, 337.
_pustula_, 492.
_pustularis_, 235, 493.
_pyramidalis_, 494.
quadrivittatus, 284.
_radiatus_, 242, 494, 495.
_rhomboicus_, 494.
_roseus_, 279.
_rugosus_, 261.
_sagittata_, 493.
_Scoticus_, 256.
_semiplicatus_, 494.
_spongeosus_, 308.
spongicola, 225.
_spongites_, 308.
_squamosus_, 328, 494.
_stalactiferus_, 329.
_stellaris_, 494.
_striatus_, 494.
stultus, 216.
_sublævis_, 493.
_sulcatinus_, 293.
_sulcatus_, 256, 493.
terebratus, 285.
_tertiarius_, 494.
_tesselatus_, 256, 494.
tintinnabulum, 194.
varieties of, 201.
tintinnabulum, eyes of, 93.
nervous system of, 92.
cementing apparatus of, 147.
_tintinnabulum_, 195, 204, 206, 214, 493.
trigonus, 223.
_tulipa_, 195, 205, 277, 494.
tulipiformis, 204.
_Uddevallensis_, 277, 494.
unguiformis, 296.
varians, 298.
_verruca_, 518.
vestitus, 286.
vinaceus, 213.
_virgatus_, 494.
_vulgaris_, 267.
_zonarius_, 235, 494.

Ball, Dr., on the attachment of Chelonobia, 392.

Basis of shell, 49.
cancellated in Bal. lævis, 230.
perforated in Bal. terebratus, 285.
hardly distinguishable in Bal. flosculus, 291.
affected by adhering to corals, 301.
surrounded by a ledge in Chthamalus, 452, 466, 467.

Bate, Mr. C., on the spermatozoa of cirripedes, 99.
on the larva of cirripedes, 103.
on the excavation of Verruca, 514, 518.

Bisexuality of cirripedes, 23.

Boring powers of, in Verruca, 512.
in Alcippe, 549.

_Boscia_, genus, 354.

Bosquet, M., Monographie, &c. 526.

Branchiæ, 63.
in Alcippe, 537.

Brewster, Sir D., on lime and animal matter, 552.

Bristles on membranes of shell and operculum, 59.

Bronn, list of Balanidæ in his Index Palæont., 173.

Burmeister on the rank of cirripedes, 17.
branchiæ of Coronula, 64.
labrum of Coronula, 77.
reproductive system of cirripedes, 97, 100.
larvæ in the second stage, 109.
larvæ in the last stage, 114.

Cæca, ovarian, 100.
to stomach, 85.

Calcar tergi, 52.

Caligus, nerves of, 88.

Canal, alimentary, 85.

Carapace, homologies of, 131.
of pupa, 112.
aborted in Proteolepas, 595, 603.

Carina, posterior compartment of shell, 39.

Catophragmus, genus, 485.
connecting link between the Balanidæ and Lepadidæ, 41.
imbricatus, 490.
polymerus, 487.

Cement, tube of, proceeding from the pupal antennæ, 118.

Cementing apparatus in the pupa, 118, 122.
in the mature animal, 133.
in Platylepas, 426.
in Xenobalanus, 442.
in Proteolepas, 599.
organs of, in crustacea, 151.

_Cetopirus_, genus, 397.

Chamæsipho, genus, 470.
columna, 470.
scutelliformis, 472.

Changes during growth in the Balanidæ, 128, 189.

Characters, variability of, 155, 184, 197.
value of, in the Balanidæ, 154.

Chelonobia, genus, 382.
caretta, 394.
patula, 396.
cementing apparatus of, 145.
_Savignii_, 392.
testudinaria, 392.

_Chirona_, genus, 177.

Chitine, 7, 58.

Chthamalinæ, sub-family of, 446.
characters of, 152.

Chthamalus, genus, 447.
antennatus, 460.
cirratus, 461.
dentatus, 463.
fissus, 462.
_giganteus_, 477, 192.
_glaber_, 455.
Hembeli, 465.
intertextus, 467.
scabrosus, 468.
stellatus, 455.
_stellatus_, 492.

Ciliæ, not present in the articulata, 516.

Circulation, 87.

Cirri, their muscles and movements, 71.
their structure, 81.
their reparation, 158.
in Acasta, with variable hook-like teeth, 306, 311.
antenniformed in Chthamalus, 453, 460.
variability in numbers of segments in Tetraclita porosa, 332.
structure of, variable in Chamæsipho columna, 472.
with one ramus, converted into a triturating button in Alcippe, 542.
abdominal in Cryptophialus, 575.
none in Proteolepas, 587.

Cirripedia, their rank and affinities, 10 to 20.

Cirripedes, how their position is acquired, 127.
young, changes in, 128.
sessile, 33.

_Clisia_, genus, 496.
_striata_, 519.